With a working vehicle such as a wheel loader, an output of an engine is used as power for working and power for traveling. With a wheel loader, a load such as earth or sand or the like is scooped up with a bucket, and is loaded onto a bed of a truck or the like. Thus, in the prior art, it is necessary to consider the balance between traveling speed of the wheel loader and raising speed of the bucket, and clutch pressure is controlled so as to maintain the traveling speed at a constant speed during loading work (refer to Patent Document #1).
It should be understood that techniques are known for implementing constant speed traveling by controlling a throttle opening amount of an engine (refer to Patent Document #2), and for restricting vehicle speed control during an interval from the start of dragging of a clutch until the clutch is completely engaged (refer to Patent Document #3), although there is no such prior art particularly related to a working vehicle.    Patent Document #1: Japanese Laid-Open Patent Publication Heisei 11-181841;    Patent Document #2: Japanese Laid-Open Patent Publication 2000-118264;    Patent Document #3: Japanese Laid-Open Patent Publication 2004-299415.